The present invention generally relates to wireless communication networks, and particularly relates to dormant handoff of mobile stations having multiple packet data service instances.
In a cdma2000 network, Packet Data Serving Nodes (PDSNs) establish, maintain, and terminate Point-to-Point Protocol (PPP) sessions for mobile stations supported by the network. In this role, PDSNs carry packet data between one or more Public Data Networks (PDNs), e.g., the Internet, and the mobile stations. Each PDSN routes packet data for mobile stations supported by a particular group of Base Stations (BSs). Entities referred to as Packet Control Functions (PCFs) provide the Radio-Packet (RP) interface between the BSs and the PDSN.
PCFs provide a number of functions supporting the RP interface, including managing the packet data states (active, dormant) of mobile stations, relaying packets between the mobile stations and the PDSNs, buffering data received from PDSNs for dormant mobile stations, supporting handovers, and PDSN selection. In some architectures, each BS, including a Base Station Controller (BSC), includes integrated PCF logic so that, effectively, each BS interfaces to an associated PDSN through its own PCF. In other architectures, each PCF interfaces a number of BSCs to one or more PDSNs. In either case, the radio service area or “footprint” associated with each PCF defines a packet zone that is identified uniquely in the network by the combination of a System ID (SID), a Network ID (NID), and a Packet Zone ID (PZID).
To properly route packet data, a given PDSN must know the current location of each mobile station that has a packet data session established with it, which, from the perspective of the PDSN, is tantamount to keeping track of the mobile station's serving PCF. A packet data session is the set of one or more packet data service instances in use at the RAN/PDSN for the mobile station. Therefore, as part of mobility management operations, cdma2000 networks require mobile stations to re-register with supporting PDSNs as the mobile stations move across packet zone boundaries. BSs broadcast SID/NID/PZID information on their overhead channels to keep mobile stations appraised of the SID/NID/PZID values for each service area. Mobile stations that are not active (on a traffic channel) detect their changing service locations by monitoring these overhead channels. In cdma2000 networks, such end-to-end packet data support is defined by several relevant standards in the cdma2000 family of standards (e.g., IS-707, IS-2000, IS-2001, and IS-835).
The first time a mobile station connects to a PDSN, a PPP session is established between the PDSN and the PCF as part of packet data call setup. Once a PPP session has been established for the mobile station, it remains connected to the network and subsequent transmissions between the PDSN and the mobile station can be initiated by the PDSN or by the mobile station over the PPP connection. However, despite the PPP connection being “on,” the network tears down certain resources associated with that connection if no packet data is sent to or received from the mobile station for longer than a certain period of time. For example, the network tears down packet data radio links to the mobile station and tears down packet data traffic connections between the BS and PCF associated with the mobile station after the mobile station's packet data connection has been inactive for some period of time. A mobile station is considered “dormant” from the packet data perspective when all packet data service instances associated with it are dormant.
However, to keep the network apprised of movement affecting packet data routing, dormant mobile stations still must re-register with their supporting PDSNs as they move between different packet zones. This re-registration process is referred to as dormant (packet data) handoff and all mobile stations having dormant packet data sessions with the network perform dormant handoff responsive to recognizing movement between packet zones. Note that a mobile station can remain dormant from the packet data perspective even if it is engaged in an active voice call, i.e., whether a mobile station has radio links and a dedicated traffic channel allocated to it for circuit-switched voice service is immaterial to its packet data dormant status.
While the mobile station having or not having a voice traffic channel allocated to it does not affect its dormancy status, the presence or absence of that traffic channel does affect the mechanics of dormant handoff. If a dormant mobile station does not have a dedicated traffic channel allocated to it, it performs dormant handoff by transmitting an Origination message to a supporting BS using a common access channel available for use by all mobile stations in that service area. Receipt of the Origination message initiates some inter-entity signaling between the BS and an associated Mobile Switching Center (MSC) and between the BS/PCF/PDSN chain of network entities as part of packet data re-registration. If the mobile station has a dedicated traffic channel, it re-registers by transmitting an Enhanced Origination message (EOM) over the existing traffic channel, thereby avoiding use of the common access channel.
As a point of interest regarding re-registration, it should be noted that IS-2000 standards permit an individual mobile station to have multiple (up to six) packet data “service instances” per data session. The use of multiple service instances permits different data treatment for different packet data streams, e.g., it permits different Qualities of Service (QoS) for different types of packet data flowing between the network and a given mobile station. In some sense, this is tantamount to each mobile station having up to six packet data connections to the network (although all service instances share the same PPP connection). Indeed, each active packet data service instance for a given mobile station is assigned its own A8 and A10 traffic connections between the BSC and PCF, and between the PCF and the PDSN, respectively.
Current and past generation IS-2000 mobile stations treat each service instance like a separate data session inasmuch as these mobile stations perform dormant handoff re-registration for each service instance allocated to them. Thus, a mobile station having six service instances performs six dormant handoffs, one for each service instance, each time it crosses packet zone boundaries. If the mobile station does not have a dedicated traffic channel allocated to it when dormant handoff occurs, it sends an Origination message on the common access channel for each service instance, and all of the attendant BS/MSC signaling is repeated for each one of the received Origination messages. In this sense, then, a dormant mobile station with multiple service instances burdens the network to the same extent as a like multiple of individual mobile stations each having one service instance.